Gearless differential



Sept. 8, 1953 R. R. RANDALL GEARLESS DIFFERENTIAL Filed July 14, 195o 4Sheets-Sheet` l E 1E: L

ErIE- QILSGL INVENTOR @4A/@WL Spt. 8, 1953 R. R. RANDALL 2,651,21J4

GEARLESS DIFFERENTIAL Filed July 14, 1950 ZELE; .la 64 65 7/ 667a 62Afro/swims y Sept 8 1953 R. R. RANDALL 2,651,214

- GEARLEss DIFFERENTI@J Filed July 14, 1950 4 Sheets-Sheet 4 B. wzf

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Patented Sept. 8, 1953 2,651,214 GEARLESS DIFFERENTIAL Ralph R. Randall,Free troit Safety Clutch C port, Ill., assignor to Deporation, Detroit,Mich.,

a corporation of Michigan v Application July 14, 1950, Serial No.173,756

(Cl. 74-650) l 14 Claims.

relates to a power transmission and more particularly to a clutchcontrolled divided power flow transmission.

It is an object of this invention to provide a clutch controlled dividedpower flow transmission for driving a pair of-members which is designedsuch that both members will be positively driven even through theresistance to turning of one of the members greatly exceeds theresistance to turning on the other member. The transmission of thisinvention is, furthermore, designed to accomplish this without thedanger of a positive locking of the two driven members so that the unitis capable of differentiating the speed of the two driven members at alltimes. At the same time, my divided power flow transmission is designedsuch that, while the driving members are being driven, a greaterpercentage of the power applied is concentrated on the driven memberoffering the greatest resistance to turning.

More specifically, theinvention contemplates a divided power flowtransmission in which the power flow is controlled bya pair of clutchmembers having opposed corrugated clutch faces between which are mountedtapered radial rollers carried by the driven member. The clutch membersare designed such that positive locking with the rollers is avoided. Thepower is transmitted by utilizing the principle of roller pressureagainst an inclined plane. The clutch members and rollers are alsodesigned such that the friction therebetween will be in the form ofrolling pressure and not sliding friction. Y Other objects in the Way ofconstruction and the operation of my divided power ow transmission Willbecome apparent from the accompanying description taken in conjunctionwith the following drawings in which:

Figure 1 is a sectional view of a divided power iiow assemblyincorporating my invention and taken on a verticaly plane transverselyof the driving axis of the unit.

Figure 2 is a plan view of one of the clutch plates.

Figure 3 is a plan view of the carrier the rollers mounted thereon.

Figure 4 is a vertical section through the clutch plates.

Figure 5a isa diagrammatic View illustrating This invention cage with 2the relative positions of races of the clutchv plates movement.

Figure 5b is Vview illustrating therelative positions occupied by theinner races the rollers and outer at one stage of their positionsshownin Figure 5a. Figures 6a and 6b, '7a and 7b, 8a and 8b are diagrammaticviews similar to 5a and 5b but showing the relative positions occupiedby the clutch platesV and rollers at progressive increments of '7l/2 ofrotation of one ofthe clutch plates relative to the other.

Figures 9a. and 9b, '10a and 10b, 11aV and 1lb are diagrammatic views onan enlarged scale illustrating more vparticularly the manner in whichthe driving effort shifts from one set of races tothe other when theresistance to turning is greater on one of the clutch plates that theother. I

Figure 12 is a fragmentary sectional view similar to Figure 1 butshowing a modified form of the invention. Y

Figure 13a is a diagrammatic view of one position of the rollers andouter races of the clutch plates in the modified form of the inventionillustrated in Figure 12'. f n

Figure 13b is a diagrammatic v iew showing the relative positionsoccupled by the rollers and inraces are in the position Figuresl 14a and14h are views similar to Figures 13a and 13b showing a modied form ofrace construction.

A divided power flow transmission of my indriving a pair of members atrelative velocities and may be used in a variety of differentapplications where a device of this type is necessary. It isparticularly useful in driving the wheels of a vehicle and therefore,for the purposes of illustration, the divided power flow transmissionwill be described in a form adapted for use on an automotive vehicle. l

Referring to the drawings, the transmission assembly is -housed withlntacasing I0, which preferably comprises two cup shaped members il and I2Which are secured together as by bolts I3.` YOne of the members isprovided with an apertured ange I4 by meansof which a ring gear (notshown) maybe secured. VVThe ringgear -it .mQYeS latraux/With the trough31a ytowards the toothis't 36a on plate Ito the position illustrated inFigure'a. In so doing, roller 28a accelerates plate IS'and has rolled intrough 31a Aon plate I 6 in a direction away from the tooth crest 36a.While this movement occurs in the outer race, rollerza in the inner racerolls upwardly in trough 39a towards the crest of tooth 38a on plate I5as is illustrated in Figure 6b. ,As will be more fully explainedhereinafter, in the positions generally illustrated in Figures 6a and6b, roller 28a is being released from driving engagement with platesl5and I6 and roller 29a is now assuming a driving position relative to theclutch plates. In Figures 7d and 7b the rollers 28 in the outer racehave reached a by-passing position while the rollers 29ar in the innerrace are exerting a maximum driving pressure against both clutch plates.The positions assumed by the two sets of rollers when the drive is beingtransferred from the rollers in the inner race to the rollers in theouter race are shown diagrammatically in Figures 8a and 8b.

It will be noted in the arrangement illustrated the distance betweensuccessiveteeth. This is necessary since the average velocity of thefaster moving clutch plate is twice the velocity of the carrier cage.

I have determined that by proper design of the teeth and indentations onthe clutch plates, the unit .will drive both driven members withoutlocking even though the resistance to turning on one of the membersgreatly exceeds the other. It is probable that locking of the memberswould occur if the driving. angle between the roller and the clutchplates, that is, the angle between the tangent at the point of contactand the plane of rotation of the clutch plates, falls below a wedgingangle of about while the roller is in driving relation with the clutchplate. This type of locking, due to 'wedging, is avoided in my unit bydesigning vthe teeth and indentations on the races ofthe clutch platessuch that, when the driving angles between one set of rollers and theclutch plates approach a wedging angle,

the other set of rollers comes into driving relation and the first setof rollers by-passes the teeth on the clutch plate with no apparentdriving effort.

It is believed that this shifting o f the driving eifort from one set ofrollers to the others is illustrated more clearly in Figures 9c through11b. It will be noted rfrom these illustrations that the radius Rt oftroughs 3'I is greater than the radius Re of the tooth crests 3B on the4outer race and that the radius n of troughs 39 is greater than theradius rc of tooth crests 38 Ion the inner race. It will also be notedthat the radius R. of rollers 28 is greater than Re the radius r of therollers 29 is greater than rc and less than rt.

Assuming for the purposes of illustration that the rollers 28 in theouter race are disposed in the driving positions illustrated in Figure9a, then the rollers 29 in the inner race are disposed in the by-passingposition illustrated in Figure 9b. Then if a driving torque is appliedto carrier cage 24 in the direction indicated by the arrow and plate I5is restrained from rotating, roller 28 will roll along the surfacegenerated by Re on plate I5 towards the crest'of tooth 36 and, insodoing, the opposite sideAv o f the and less than Rt and thatl rollerrolling towards the base of trough 31 on thesurface generated by Rt onplate I6, thus driving plate I6 forwardly. At the same time, roller' 29on the inner race rolls on plate I5 along the movement of roller 28 androllers 29 now assume a pressure contacting relation with the clutchplates and rollers 28 are relieved from driving pressure.

Angles a, b, c and d are all greater than 10, which I have assumed to bethe minimum driving angle Vbeyond which the plates I5 and I6 would belocked together because of the wedging action of the rollers.

crests these minimum .driving angles can be controlled.

It will be observed that, as rollers 28 and 29 plate I 6 will be greaterthan the tendency for roller 28 to accelerate plate I6. y Thereforeroller 29 will assume a driving relation with the plates, `and roller 28will be relieved of driving pressure and will assume a condition ofby-passing in relation to the plates. `In rolling from ure lla, plate I6is emmen@ levedigedihitslight accelerating and decelerating movement ofthe one plate when the other is held rigid by testing the -un'it on adynamometer.

It will be noted that Figure 11b roller 29 is in the position occupiedby roller 28 in Figure 9a and that the roller 29Y will continue to exertdriving pressure on the clutch plates until it reaches thepositionoccupied byA roller 2B in Figure a.

With the above description oi fthe driving relationship of the rollersand plates, it is believed that the reason why both driven members, thatis, both clutch plates, will be driven even though the resistance toturning on one member greatly exceeds the resistance 'on the other willbe readily understood. It will be noted that the `dris'ring pressureexerted by the rollers on the clutch plates ris at all times inclined tothe plane `of rotation of the clutch plates.

The driving pressure may be resolved into two components, one parallelto the plane of rotation and the other perpendicular to the plane or'rotation. These force components are illustrated diagrammatically inFigure 10a and are designated m and n, respectively. The component 'm ofpressure p tends to rotate the clutch plates but the component n urgesthe clutch plates apart against the bearing plates I9. The friction atthe faces of bearing plates I9 tends to resist relative rotation betweenlthe clutch plates on the one hand and housing members il and l2 on theother hand. Therefore as long as the frictional drag on one of theclutch plates exceeds the tendency for the rollers to drive that platefaster than the housing I0 is being driven, both the clutch plates andthe housing will be driven at the same speed and will `rotate as a unit.Translated into terms of practical eiiect, this means that when used ona vehicle, and the traction on the two drivenwheels differ, both wheelswill be rotated at substantially the same speed as long as the combinedresistance produced by the traction on the wheel of least traction andthe frictional drag on the corresponding clutch plate exceed thetendency for the rollers to accelerate that clutch plate over the other.The maximum outward force on the clutch plates is, of course, determinedby the minimum driving angles of the rollers; the shallower the rollers,the greater the outwardforce and therefore the greater the disparity intraction permissible -on the two driven wheels before one wheel willspin. The smoothness and nature of the faces of bearing plates I9, will,of course, also control to a certain extent the maximum ratio of theresistance on the two clutch plates in which spinning isavoided sincethe nature of these faces determines the fractional drag on the clutchplates.

It will be appreciated that as long as the traction on the two wheels iswithin a ratio which causes both wheels to rotate together, the wheel oileast traction is unable to utilize half of the available power andtherefore the'wheel having the greater traction will receive the greaterpercentage of the `driving torque.

Inactual tests of my divided power flow transfmission, a unit oi thetype described was lern-- ployed` as a differential in a militaryvehicle equipped witha motor rated to deliver 100 it. The outerdiameterof the housing i0 was The clutch plates were 35%" in'diameter The majorradius of hile the major radius The 4a". with 9 teeth in each series,Vthe tooth 'crest was .184

of the concave indentation' was .7868".

large rollers had a mean diameter of about 1%" while the small rollershad 'a mean diameter of about si". The unit was subjected to a braketest in which a constant load of k38 pounds was applied to one wheel andon the other wheel a load of 38 pounds wasapplied and decreasedapproximately 5 pounds at a time. Both wheels rotated until the load ,onthe one wheel was reduced to 6 .pounds at which reading the wheel loadedwith38 pounds stopped rotating and the wheel loaded with 6 poundsrotated at an increased velocity. It will be Anoted that the ratio ofthe loads on the two wheels before the one wheel spun is approximately6%, to l. As was previously explained, 'this ratio can be varied bycontrolling the relative radii of the tooth crests and troughs; Vbutappreciated, however, that the greater this ratio, the greater will bethe tendency for the unit to lock.

It will be appreciated that by em loying rollers for transmitting thetorque from the carrier cage to the clutch plates, the unit stressesencountered are much less than those that would result if balls orsliding pinswere used in place of rollers. In applications designed forexcessively high torque where the size of the transmission casing islimited because of other design factors, the unit pressure encounteredon the rollers in the form of the-invention illustrated in Figures lthrough 8b, may approach the crushing limit of the rollers and there is,therefore, illustrated in Figures 12 through 13b a modiiied `form of theinvention. In this modification, instead of employing a series of singlerollers in each of the outer and inner races, the rollers are arrangedin pairs.

As is illustrated in Figure 1-2, the series of rollers in the outerraces oi the clutch plates are arranged as paired rollers 45 and 46, andthe rollers in the inner race'sare arranged in pairs 41 and 48. Theserollers are supported by carrier cage 49 so that the-axes of the rollersintersect at the axis of rotation of carrier cage 49. The lugs yEil,between which the rollers are seated, are such as to vapply a radialpressure to both rollers in each pair in a direction parallel to theplane of rotation of carrier cage 4B. The pressure exerted by the lugsis, therefore, divided rbetween the rollers 'in each pair and the unitstress is therebymaintained Within safe limits. The corrugationsy 5IVand 52 on the inner and outer races of clutch plates 53 and 54preferably corre- Spond with the inclination of the tapered surfaces ofrollers 45, 46, 41 and 48 in the same manner Aas previously describedwith reference to Figure l so that the rollers maintain a true radialmovement withrespect to the axis of rotation of carrier cage 49,

The'operation of the kdivided power flow transmission illustrated inFigures 12 through 13b is substantialiy'the same as'that described withreference to Figures 1 through 1lb. When the rollers in either the outeror the inner races are in the lay-passing position, the rollers in theother race are exerting a maximum torque on both clutch plates. Ii one'clutch .plate offers 'greater resistance to turning than 'the other,then the rollers tend to by-pass the corrugations on the clutch plateoffering the greatest resistance to rotation in 'the sameV manner aspreviously described. VClutch, plates 53 and 54 are spaced apart Vandthe .radii of corrugations 5| and 52 are controlled such that thedriving contact angle of the rollers against the inclined faces of thecorrugations falls at all times above 10, and preferably above=l2-Y`With the Ydriving contact angle limited in this manner wedging orlocking is prevented. f

i In Figures 14a and 14h, a modified form of construction for the racesof the clutch plates is shown. In Figure 14a the relative positions ofthe rollers in the outer race are shown when the rollers in the innerraceoccupy the positions shown in Figure 14b. The clutch platesdesignated as 62 and 63 are substantially the same as clutch plates land I6 previously described except for the races. In this modication theinner and outer ra-ces are each formed with alternately inclined faces,l64 and I65 on the outer races and 66 and 61 on the inner races. Theseinclined faces are inclined relative to each other and also to thevertical plane of carrier 68 so as to correspond with the taperedsurfaces of frustoconical rollers 69 and 'I0 in the outer and innerraces, respectively. Each adjacent pair of inclined faces 64 and 65intersect to form a crest 1| and a trough 12. Faces 66 and `6'! on theinner races provide crests 13 and troughs 14. The radii at the toothcrests and at the base of the corrugations are controlled such as toproduce the desired driving relationship of the rollers and clutchplates while maintaining the driving angle greater than a wedging angle.

It will thus be seenthat I have provided a divided power flowtransmission which has Very desirable operating features. The drivingangles between the rollers and the teeth on the clutch My device isfurthermore very compact, and a unit of relatively small size is capableof transmitting a very large torque. This feature is especiallyadvantageous when the unit is used as a differential on a motor vehiclewhere size is oftentimes a limiting factor. One of the features tingdevices. These rollers present a relatively large contact area ascompared with balls and, at the same time, they avoid the undesirablesliding friction and wear encountered individed power direction, thecarrier cage will be rotated at a reduced velocity with only a slightcounter rotational torque on the clutch plate being held.

l0 cage 24 are nstaggered' circumferentially, then it will beappreciated that the position of the crests and troughs on one racerelative to the crests entially offset.

tween a set plates, said sufficient to of corresponding races on saidclutch clutch plates being spaced apart only permit the rollers to rollbetween the corrugations being formed with frusto-conical surfaces atthe trough and crest portions thereof, the surfaces of said crests andtroughs and said rollers being generated by a, line passing through theaxial center of said carrier plate whereby said rollers maintain rollingline contact with said crests and troughs at all times, said carrierplate being keyedv to rotate with said housing, the faces of said clutchplates opposite said races being fashioned to exert pressure against theend wallsV of said housing and thereby prevent said clutch plates fromfreely rotating in said housing under the influence of said rollers.

2. The combination set forth in claim 1 including bearing meansinterposed between said clutch plates and said end walls of saidhousing, said bearing means providing a, limited frictional engagementbetween said clutch plates and said end Walls.

3. A divided power flow transmission comprising a pair of axiallyaligned clutch plates spaced apart and in face to face relation, saidplates each having at least two concentric and radially spaced annularraces on the opposing faces thereof, each of said races having a seriesof radially extending depressions intersecting to form a radiallyextending beveled tooth, said depressions being arranged such that whenthe teeth on a corresponding set of races on said clutch plates arediametrically opposed, the teeth on another set of corresponding racesare circumferentially offset relative to each other, a, carrier platepositioned between the opposing faces of said clutch plates and coaxialtherewith, said carrier plate having a plurality of radial recessestherein and at least two annular series of frusto-conical rollers seatedin said recesses, said series of rollers being spaced are positionedrelative to each other such that when the teeth of a corresponding setof races are diametrically opposed, the axis of each roller in said setof corresponding races is spaced from one set of opposed teeth onequarter the distance between successive pairs of opposed teeth, saidclutch plates being spaced apart only sufficient to permit the rollersto roll freely between the beveled faces of said opposing races in anundulating path circumferentially of said clutch plates.

4. The combination set forth in claim 3 wherein said teeth and saidfaces of said depressions are beveled to correspond with the taperedouter surface of said rollers so as to maintain line contact with thesurface of said rolers.

5. The combination set forth in claim 3 wherein said teeth and the facesof said depressions are beveled to correspond with the tapered surfaceof said rollers whereby the rollers maintain line contact with sa'dteeth and depressions and retain a true radial position relative to theaxis of said carrier plate.

6. A divided power flow transmission comprising a driving member and apair of driven members, said driving member comprising a rotatablecarrier plate having a plurality of radially extending frusto-conicalrollers positioned thereon for movement in a plane transversely of theplane of said plate, said rollers being arranged in at least two annularradially spaced series, said driven members comprising a pair of clutchplates positioned coaxially with said carrier plate on opposite sidesthereof, each of said clutch plates having concentric annular racesthereon spaced radially to correspond with the annular series of rollerson said carrier plate, said races being corrugated, the crest of thecorrugations forming radially extending teeth, said corrugations beingspaced around each race such that when the crests on a corresponding setof races are diametrically opposed, the crests on another set ofcorresponding races are circumferentially offset relative to each other,whereby, when the rollers in one set of races are disposed between thecrests on one race and the center of the troughs on the other race, therollers in another set of corresponding races are driving relation withthe corrugations on said other set of races, said plates being spacedapart `iust sufficient to permit said rollers to roll freely between thecrest of a corrugation on one plate and the center of the trough of acorrugation on the other plate, said corrugations being beveled suchthat the rollers maintain line contact with the corrugations on both ofsaid clutch plates.

'7. The combination set forth in claim 6 including a housing and whereinsaid clutch plates are rotatably supported within said housing, saidclutch plates being arranged to exert pressure in a directiontransversely of the plane thereof against the end walls of said housing.

8. The combination set forth in claim 6 wherein said clutch plates arespaced apart and the relative radii of said tooth crests and the troughsof said corrugations are such that the contact angle between a rollerand the surfaces of said races relative to the plane of said carrierplate is maintained above 10 when the roller is in driving relation withsaid races.

9. The combination set forth in claim 6 wherein the rollers in each ofsaid series are arranged in pairs, the rollers in each pair beingdisposed side by side with their axes spaced transversely of the planeof said carrier plate and with their adjacent surfaces in line Contact.

10. The combination set forth in claim 6 wherein said corrugations aretriangularly shaped.

11. The combination set forth in claim 6 wherein the troughs and crestsof said corrugations are provided with frusto-conically shaped surfacesover which said rollers roll.

12. A divided power flow transmission comprising a pair of axiallyaligned clutch plates spaced apart and in face to face relation, saidplates each having at least two concentric and radially spaced annularraces on the opposing faces thereof, each of said races having a seriesof radially extending depressions intersecting to form a radiallyextending beveled tooth, said depressions being arranged such that whenthe teeth on a corresponding set of races on said clutch plates arediametrically opposed, the teeth on another set of corresponding racesare circumferentially offset relative to each other, a carrier platepositioned between the opposing faces of said clutch plates and coaxialtherewith, said carrier plate having a plurality of radial recessestherein and at least two annular series of frusto-conical rollers seatedin said recesses, said series of rollers being spaced apart tocorrespond with the radial spacing of said races, said rollers beingseated on said carrier plate for movement freely in a plane transverselyof the plane of said carrier plate, said clutch plates being spacedapart only sulcient to permit the rollers to roll freely between thebeveled faces of said opposing races in an undulating Ypathcircumferentially of said clutch plates, the teeth in each of said racesbeing spaced apart such that the included angles between successiveteeth are the same in both races.

13. A divided power flow transmission comprising a pair of axiallyaligned clutch plates spaced apart and in face to face relation, saidplates each having at least two concentric and radially spaced annularraces on the opposing faces thereof, each of said races having a seriesof radially extending depressions intersecting to form a radiallyextending beveled tooth, said depressions being arranged such that whenthe teeth on a corresponding set of races on said clutch plates arediametrically opposed, the teeth on another set of corresponding racesare circumierentially offset relative to each other, a carrier platepositioned between the opposing faces of said clutch plates and coaxialtherewith, said carrier plate having a plurality of radial recessestherein and at least two annular series of frusto-conical rollers seatedin said recesses, said series of rollers being spaced apart tocorrespond with the radial spacing of said races, said rollers beingseated on said carrier plate for movement freely in a plane transverselyof the plane of said carrier plate, said clutch plates being spacedapart only sufiicient to permit the rollers to roll freely between thebeveled faces of said opposing races in an undulating pathcircumferentially of said clutch plates, the number of rollers and teethin each race are proportioned in a ratio of at least three teeth to tworollers.

14. A divided power flow transmission comprising a driving member and apair of driven members, said driving member comprising a rotatablecarrier plate having a plurality of radially extending frusto-concalrollers positioned thereon for movement .in a plane transversely of theplane of said plate, said rollers being arranged in at least two annularradially spaced series, said driven members comprising a pair of clutchplates positioned coaxially with said carrier plate on opposite sidesthereof, each of said clutch plates having concentric annular racesthereon spaced radially to correspond with the annular series of rollerson said carrier plate, said races being corrugated, the crest of thecorrugations RALPH R. RANDALL.

References Cited in the flle of this patent Number 5 1,283,283 1,568,3581,857,978 1,897,555

Number UNITED STATES PATENTS Name Date Patch Oct. 29, 1918 Welsh Jan. 5,1926 Robbins May 10, 1932 Ford Feb. 14, 1933 FOREIGN PATENTS CountryDate Switzerland Oct. 31, 1935 Germany July 19, 1919 Great Britain June28, 1935

